Experts have implemented a management and conservation strategy program for economically important brown algae, taking into account its economic and social significance, as well as the significant increase in algae harvest. The prospect of this program is focused on the surveillance of available and harvable biomass, the assessment of the strength of the harvest (Capture Per Union Effort – CPUE) and characterization of the production chain based on these primary producers. As a result of this strategy maintained since 2010 and several years of algae knowledge, recommendations have been made for the management of algae sustainability. The premise here is how to harvest is more important than how much you harvest. This program has been implemented in three Chilean conservation instruments at country level, representing three different conservation strategies and these are:
Marine protected areas (marine park, marine protected area),
Open access areas (OAA) for artisan fishermen, where they collect and harvest marine resources,
• Management areas for the exploitation of benthic resources (MAEBR),
Here are places where organized fishermen have some territorial rights over a coastal zone. The conservation strategy in MAERB is based on joint management. The main practical recommendations of the program for the sustainability of brown algae focus on selectively harvesting adult sporophytes and maintaining a permanent stock of individuals capable of breeding. It also focused on facilitating recruitment, reducing grazing by benthic invertebrates, and allowing algae sustainability. Considering all the points stated, bio-ecological recommendations should be applied to algae beds that are important, frequent and subject to heavy harvesting, and they are as follows:
Harvesting the whole plant including holdfast,
• Harvesting plants with a basal diameter greater than 20 cm,
• Harvesting one out of every three plants by choosing the largest specimens and thus thinning the population,
For the Macrocystis special case, cutting the canopy to one meter below the surface,
According to the management regime (Conservation Strategy) assigned to natural populations by the competent authority, both the density of adult plants and the young breeding of Lessonia nigrescens are subject to temporal change. In marine protected areas such as marine parks or marine reserves (MPA), annual regeneration of algae populations exhibits a seasonal cycle in which the natural deaths of adults are compensated by heavy youth employment. In MAEBR, the density of adult plants decreases preferably during the maximum harvest period sustained in spring and summer. In these conditions, the annual cycle of algae regeneration is maintained by recruiting young plants after harvest.
In OAA, where algae harvest occurs throughout the year, adult plant density has decreased significantly. Therefore, the continuous release of the substrate through continuous harvesting facilitates the recruitment of permanent young people. This significantly increases the intensity of recruitment throughout the year. The last population renewal process occurs regardless of seasonal change, unlike what is observed in Lessonia populations of the Conservation Strategies of MAEBR and MPA. The density of adult plants is highest in populations within MPA as opposed to those in OAA. As previously exposed in MAEBR, the seasonal harvest of Lessonia reduces the density of adults. However, this effect of the harvest is significantly lower than that observed in OAA.
In these open-access areas, the density of adult plants is less due to the high harvest pressure, causing the stock of breeding plants to shrink and therefore negatively impacting algae regeneration. There is an exception to this model observed in OAA populations where the difficulty of access to the shoreline is an obstacle to permanent harvest. In this case, topography constraints to access produce effects that mimic some kind of natural co-management. Thus, the size distribution pattern of Lessonia plants in OAA is quite similar to the model observed in MAERB. As MPA, Lessonia yield (kg / m 2 of biomass) is constant throughout the annual cycle and is close to 50 kg / m 2. In contrast, the biomass available in MAEBR evidence points to seasonality with the annual regeneration cycle of algae in the spring and summer after harvest. A similar trend is observed in OAA, with significantly less biomass available, which does not exceed 25 kg / m.
Available biomass is the largest in MPA populations and lowest in OAA populations. In MAEBR and OAA, available biomass is 50% and 65% lower than stocks in MPA, respectively. The available biomass in MAEBR represents the permitted limit for sustainable use of algae forests and is proof of adequate implementation of the management plan. On the other hand, the current level of biomass in OAA is an indicator of highly abused populations. And the management program helps establish sustainability parameters that deal with strong harvest pressure.
The size structure of the Lessonia nigrescens populations varies according to the proposed morphological variables, the management and protection measures applied. In MPA, 20% of the populations are beginners, 35% are young, and the rest of the population are adults with large sized plants. In MAEBR and OAA, hired persons represent 35% of the entire population, while young plants represent 45% and 55% respectively. In MAEBR, the fraction of adult plants is replenished with the growth of young plants during the annual cycle, while in OAA, the strong harvest pressure facilitates the collection and colonization of free primary substrate. In MPA, the share of adult plants suitable for harvest is generally 45% of the population. In MAEBR, the harvable part corresponds to 25% of the total biomass available. In contrast, in OAA, the biomass available for commercial harvest did not exceed 10% of the total plants in the entire Lessonia population studied in northern Chile.
After 25 years of observation and evaluation of Lessonia populations, thousands of hours of field monitoring and the production of abundant literature, and based on the bio-ecological information obtained, the main concept associated with the recommendations for the sustainable management of the Lessonia nigrescens complex is more important than how much you harvest. This practice of resource management has spread among fishermen over the last 15 years and has been voluntarily adopted as an alternative to the traditional precautionary method that the fishing authority has set a catch quota. And it arises from the total available biomass. However, fulfilling the aforementioned premise requires good practice for artisan fishermen who are the only authorized users to harvest brown algae in Chile.
The correct implementation of MAEBR’s management advice appears to be strongly correlated with the social capital generated by the joint management. This is a concept that does not make sense in OAA where the harvesting activity is individual and difficult to implement. The wide transverse expansion of the coastal zone and the various restrictions on access to it increase the cost of implementation and reduce the effectiveness of control of the fishing authority. Thus, as in many, if not all cases, participatory awareness is a key factor in the conservation of natural populations of Chilean kelps and the sustainability of this resource. However, some recommendations are given and these are as follows:
• Perfecting commercial management capacities by using social capital,
• Significant progress in areas such as the optimization of inspection mechanisms and sanctions, taking into account the unique characteristics of the Chilean artisanal fishers,
• Improving the flow of information between and between different actors and authorities in the production chain,
• Establishing controlled extraction of brown algae using management plans from a regional perspective,
A participatory, adaptable and multidisciplinary management plan requires ecological indicators that permanently monitor administrative measures decided directly by its users. Given these ecological indicators, brown algae can be selected from administrative measures such as harvested volume, capture per effort amount and minimum legal size of catch. The harvested volume descend is an easy to track and verify indicator. But it requires an efficient, participatory recording system in real time, allowing information to be accessed and used at the right time. Catching and minimum legal size per effort are relatively more complex indicators to monitor and enforce, as they depend on the interests of fishermen. These indicators are useful tools for setting harvest quotas, creating rotation areas, or establishing mineral extraction or biological bans.
The impact of harvest in OAA is explained by the absence of precautionary management measures in the high demand scenario for biomass. Therefore, management based on the ecosystem approach needs to be observed and communicated by both scientific observers and artisan fishermen. In addition, they are ecological indicators sensitive to harvest pressure that allow easy-to-measure decision criteria to be established. Demographic characteristics such as density of adult plants, biomass per area, recruitment and size structure all constitute indicators that meet these characteristics. It is easy to obtain and can be evaluated along spatial and temporal gradients.
Based on demographic indicators, the rule determines that harvesting in OAA should begin when the abundance and biomass of one population per unit of area is close to the biomass or demographic levels detected in an uninterrupted population. The minimum intensity of recruitment, the proportion of adult plants should be above 40% of the total population. And the percentage of adult plants remaining in the area should be sufficient for post-harvest recruitment. Then, when the population reaches levels of abundance and biomass per unit of area similar to the population under heavy harvest pressure, its sustainability depends on some. These elements are as follows:
• Stability of recruitment frequency,
• Preserving the breeding stock of individuals,
• The stability of the harvesting frequency,
These indicators should expire when they exceed the harvest period and follow an interim period (prohibition or quotas) until adequate pre-harvest values are reached. Thus, the establishment of a permanent monitoring program for the Lessonia nigrescens population allows using complex, demographic indicators in OAA and MAEBR. These indicators are as follows:
• Verification of the implementation of management plans,
• Determination of harmful effects on population dynamics caused by exogenous disturbances during harvest,
• The time required for the restoration of the respect forest to optimum harvest levels,
• Determination of extraction quotas according to the sector,
• Establishing expulsion bans in a just, participatory and local manner,
Author: Ozlem Guvenc Agaoglu